Imino-substituted esters of dithiocarbamic acids



Patented Aug. 26, 1952 7 UNITED STATE IMINO-SUBSTITUTED ES'TERS F DITHIO- CARBAMIC ACIDS Roger A. Mathes, Akron, Ohio, assignor to The B. F. Goodrich Company, New York, N. Y., a

corporation of New York Application January 28, 1950, Serial No. 141,167

No Drawing.

4 Claims.

This invention relates to a new class of chemical compounds useful as accelerators for the vulcanization of natural and synthetic rubbers and for various other purposes, and pertains more specifically to novel dithiocarbamic acid derivatives and a method of making the same.

The compounds of this invention are iminosubstituted esters of dithiocarmabic acids, which possess the general formula:

represents the radical derived by removing hydrogen from an amine having at least one hydrogen connected to the amine nitrogen, R represents a bivalent hydrocarbon group preferably of 1 to 6 carbon atoms and R" represents hydrogen or ahydrocarbon group preferably of 1 to 12 carbon atoms. i

These imino-substituted esters oi dithiocarbamic acids are conveniently and readily prepared'by first reacting a salt of a dithiocarbamic acid with ahalo-aldehyde to form, bymetathesis, a dlthiocarbamyl aldehyde and then reacting the dithiocarbamyl aldehyde with ammonia or a primary amine to form, by splitting out of one molecule of water, the desired imino derivative of the dithiocarbamic acid These reactions can be illustrated by the following reaction equations where W l h R R and B have the significance as described above, X represents a halogen atom and M represents the cation of the dithiocarbamic acid salt:

Reactions 1 and 2 are both spontaneous and exothermic and will proceed at room. temperature. Reaction (1) is sufficiently exothermic to require cooling for best results, but, reaction (2), while also exothermic, does not proceed at such a rate as to require cooling. In fact, without any external cooling during reaction (2) the temperature of the reaction mixture increases only about 2 C. to 5 C. over the entire reaction period.

Any salt of a dithiocarbamic acid can be employed as a reactant in the preparation of the compounds of this invention, but the watersoluble salts such as the alkali metal and ammonium salts are preferred as reactants because of the fact that they yield water-soluble inorganic halide salts as by-products in reaction (1), which salts can be easily separated from the water-insoluble organic product of the reaction. The ammonium, sodium and potassium dithiocarbamates are the most preferred watersoluble. salts because of their availability and economy of preparation. Salts of dithiocarbamic acids are ordinarily and most conveniently prepared by reacting carbon disulfide with. a primary or secondary amine in the presence of a salt forming alkaline material, and use of the relatively inexpensive sodium, potassium or ammonium hydroxide as the alkaline material is desirable; hence the dithiocarbamic acid is generally obtained in the form of a sodium, potassium or ammonium salt.

The t radical of the general formula hereinbefore set forth is that part of the dithiocarbamate which is derived from the amine employed in preparing the salt of dithiocarbamic acid. Accordingly, the dithiocarbamates which can be employed as reactants include, among others, those derived from the reaction of carbon disulfide with such primary amines as methyl amine, ethyl amine, n-propyl amine, isopropyl amine, n-butyl amine, amyl amines, lauryl amine, cyclohexyl amine, aniline, and naphthyl amine, as well as those derived from the reaction of carbon disulfide with such secondary amines as dimethyl amine, diethyl amine, di-n-propyl amine, diisopropyl amine,'dibutyl amines, diamyl amines, dicyclohexyl amine, ethyl cyclohexyl amine, ethyl amyl amine, morpholine, piperidine, diphenyl amine, ethyl aniline, di-(beta naphthyll amine, eta.

gasses Specific dithiocarbamates derived from these amines are for example sodium ethyl dithiocarbamate, sodium dimethyl dithiocarbamate, sodium N-methyl N-cyclohexyl dithiocarbamate, sodium N-cyclopentamethylene dithiocarbamate (derived from piperidine), sodium N-cyclo-ethylene-oxyethylene dithiocarbamate (derived from morpholine) sodium phenyl dithiocarbamate, sodium o-tolyl dithiocarbamate, sodium dicyclohexyl dithiocarbamate, and sodium diphenyl dithiocarbamate.

Typical halo-aldehydes having the formula where R is a divalent hydrocarbon radical, which are useful as reactants in preparing the compounds of this invention are, for example, bromoacetaldehyde, chloroacetaldehyde, Z-chloropropionaldehyd'e, l-chloropropionaldehyde, l-bromopropionaldehyde, 2 iodopropionaldehyde, l-chlorobutyraldehyde, 2-'chlorobutyraldehyde. l-bromobutyraldehyde, 2 bromobutyraldehyde, l-ch1oroisobutyraldehyde, l-bromovaleraldehyde, 3,- chlorovaleraldehyde, 1 bromocapraldehyde, l-chloroheptaldehyde, .p-chlorocyclohexane carboxaldehyde, o-, mor p-chlorobenzaldehyde, m-: or -p-bromobenzaldehyde, -chloro-o-to1ualdehyde, 2-ch1oro-p-tolualdehyde, and p-bro- The :reactions yielding the compounds of this invention can be carried out in the presence or absence of asolvent or diluent. The use of a reaction diluent is preferred, sincexthis provides a "convenient means for removal of the heat liberated by reaction (1). The use of an aqueous solution of. a Wetting agent as medium for. the reaction is especially desirable in that the product is thereby obtained in earlier-handled form. Other solvents or diluents which are commonly employed in the synthesis of organic compounds such as liquid alcohols, ethers, hydrocarbons and chlorinated hydrocarbons may also be employed in the preparation of the compounds of this invention, V

The following Example I sets forth complete detailed the preparation of 2-(phenylimino) ethyl N,-N-di-methyl di-thiocarba-mate and is given to illustrate a preferred general method of preparin the various members of the new class of compounds of this invention. The term fparts as employed in the examples which 'follow'is use to indicat parts by weight.

EXAMPLE I solved i-n 400 parts of water was added at room' 4 temperature to a reactor equipped with a stirrer, a reflux condenser and a charging line. The aqueous solution was stirred while 44 parts of chloroacetaldehyde dissolved in 100 parts of water were slowly added to the reactor ove a period of about 70 minutes. As soon as the addition of chloroaldehyde was started a reaction began as was evidenced by a rise in temperature of the reaction mixture. The reaction mixture was maintained at about C. to C. by external cooling. The product of the reaction, dimethyldithiocarbamyl acetaldehyde, formed as a precipitate of fine crystals.

To the mixture prepared above there was then added with continued stirring but without external cooling, 46.5 parts of aniline whereupon the temperature rose about 2 C. This mixture was stirred for about 20 minutes to complete the reaction. The coarse precipitate which had then formed was filtered from the reaction medium, washed with water and dried. In this manner 111 parts, a 90% yield, of a fine bull-colored powder melting at 67-72 0., identified as 2 (phenylimino) ethyl N ,N-dimethyl dithiocarbamate, was obtained.

The following Examples II and III, employing the product of ExampleI, illustrate the useof the 3 compounds of this invention to accelerate the vulcanization of natura1 and synthetic rubbers.

EXAMPLE II at $00 7; elongation, an ultimatetensile strength;

of 2800 lbs/sq. in andyan -elongation of t630 at bre 7 same ingredients with the exception of the imino dithiocarbamate and containing no other accelerator would undergo only incipient vulcanizatlon after being heated for minutes at 280 F.

EXAMPLE III A 'vuljcanizable compositionwas prepared con taining the synthetic rubber known as GR-S,

which is the product of the aqueous emulsion co-- polymerization of about parts of butadiene-l,3 and about 25 parts of styrene. This vulcanizable composition contained parts of the rubbery copolymer of butadiene-1,3 and styrene, 50 parts of carbon black, 2.5 parts of zinc oxide, 2.25 parts of sulfur, 1.0 part of phenyl-beta-naphthylamine, 10 parts of a terpeneresin acidas a softener, and 1.5 parts of 2-(phenylimino) -ethyl N,N-dimethy1-- dithiocarbamate as the vulcanization accelerator all thoroughly mixed together to form a homogeneous mass.

This vulcanizable composition was heated for r ub r: emn sit en comm-nine he -75 minutes in a .press at .280" F. and stress-strain tests were carried, out on testhstrips of the resulting .vulcanizate. In this manner it was determined .that this vulcanizate had an ultimate ten- 6 butadiene-l,3 as wellas copolymers of these conjugateddienes witheach other or with other unsaturated. compounds copolymerizable therewith such as styrene, is'obutylene, 1acrylonitri1e, methyl sile strength of 2000 lbs/sq. in. and an elonga- 5 acrylate, methyl-methacrylate, vinylidene chlotion at break of 850%. A similar vulcanizable ride, etch s composition containing the same ingredients with In general an amount of 0.1% .to 5 by weight, the exception of the imino dithiocarbamate acbased on the rubbery polymer, of theseiminocelerator and containin no other accelerator substituted dithiocarbamates will be sufiicientto would exhibit no appreciable vulcanization when 1 accelerate the vulcanization of rubbery composiheated for 75 minutes at 280 F. tions c0ntaining-0.5% to by weight of sulfur. From the results of the use of 2-(phenyl- Such compositions can be vulcanized by heating imino)-ethyl N,N-dimethyldithiocarbamate in at the ordinary vulcanization temperatures for Examples II and III, it is apparent that the dithe usual length of time. i I thiocarbamic acid derivatives of this invention The new imino-substituted dithiocarbamates are useful accelerators of the sulfur vulcanizaof this invention can also be emp asithe ti'on f rubbery at rials, I tive ingredients 'in insecticidal and fungicidal 'rhese new dithiocarbamic acid derivatives compositions. They a a s e us d as intercan be employed to accelerate the sulfur vulcanimediates in the synthesis of other Organic Chemzation of any of the various polymeric organic 16811 p nd I rubbery materials including, especially, natural The followlng Examples IV to X Set forth in and synthetic rujbbery p01ymer5 of conjugated tabular form in the table relate to other specific dienes, Examples of such organic rubbery. polymembers of this new class of dithiocarbamates. mers include the various natural crude rubbers The reactants employed to prepare each com- (which are regarded as naturally-occurring is pound are listed with the compound. The proprene polymers) and such synthetic polymeric cedural method of preparation is that described organic rubbery materials as polymers of conin Example I. Each of the compounds listed in jugated diene hydrocarbons such as butadiene-1,3, the table is effective as an accelerator of vulcaniisoprene, 2-methyl butadiene-L3, and other butazation of natural and synthetic rubbers when diene-1,3 hydrocarbons, chloroprene, and 3 cyano tested as described in Examples II and III.

:Table his)? Dithiocarbamate Ractants R-NH Compound v Product ample Halo Aldchyde aminosubstituted Esters oi Pithiocarbamic Acid) IV onofN- -sm GICHzCHQ N113 cH ;N IT L 1 ZL g S V I Z-Imino-ethyl N,N-dimethy1 ditbiocarbamate v C2H NH(I'TSNa BrCHzCHO HzNCzH: ,e1H5NH(fis-cHz01r=NctH.

2-(Ethy1imino)-ethy1 N-ethyl dithiocarbamate o12r2-o H, 0112-0111 VI 0&1; /CHz-NHI7SNa C1CH2CH2CHO HaN-(JH-CH: CH: HQNH sPCH GH CENw OHrCH, CH: Hz-CHz S (5H:

3-(isopro limin IN- 1 h l W massa e C9\H5 1H3 OHa VII N-%sNa Br-(|3CHO H1N-C H (C H N$1- s OuHs S CH: S CH:

1,1-Dimethyl-2-(hexylimiuo)-ethyl N.N-diphenyldithiocerbamate C4Hn VIII (CHa)zN("3-SNa o1-crr-o110 HflNCeH: (oHmNfi-s-c H-O 1- (n-Butyl)-2 (phenyljmino)-ethyl N N-dimethyld1th1ocarbemate Cilia CH2-CH1 Cn n GHPCHQ IX /NCSNa Cl-CH 0110110 HzNCHa /N(IJS-CH cH-oH=N oH,

CH3 S CHr-CHfl CH: g CHr-CH:

4-(Methyliminometh l-c cl 11 IN- 1 h 1- N-methyl dith i oc rl iate O exy C5115 CHrCH: CnHs CHz-CH: X NfisNa o1- CHO HzN-CH H1 c-s C2135 S Hz-CH: CzHs GHQ-CH2 p-(cyclohexylim'nometh 1)- h lN- h l-N- eth yl-dithi mr ai l i s ze p any It will-be understood that the other dithiocarb'amates, haloaldehydes and primary amines hereinbefore set forth can also be employed as reactants in preparing still other compounds of theclass of this invention. These reactants may be employed as described in Example Iand the desired product also can berecovered as therein described.

In Example I, the ratio of reactants was substantially equimolecular for all three reactants It is not critical that this ratio of reactants be employed, but rather any suitable ratio of rea'ctants can be used. These and other changes and modifications in themethod of preparation and in the resulting product will occur to those skilled in the art and are within the spirit and scope of my invention as defined in the appended claims.

I. claim:

1. A compound having the formula atoms and R" represents a member selected. from r the group consisting of hydrogen and hydrocarbon radicals containingfl to 10 carbon atoms.

2. z-(phenylimino) -eth-y1 N,N-dimethyldithiocarbamate having the formula .-3. The method of preparing an .imino-substituted ester "of a dithiocarbamic .acid which comprises reactingin solution .a water-:solubletsalt of a .dithiocarbamieacid having the formula consisting of ammonia and primary amines.

4. The method ofpreparing 2-(phenylimino)- ethyl dimethyldithiocarbamate which comprises reacting in an aqueous medium sodium-dimethyl dithiocarb'amate' with chloroacetaldehyde to form dimethyl dithiocarbamyl-acetaldehyde, and then reacting .in an aqueous medium the .diznethyl .dithiocarbamyl-acetaldehydewith aniline.

' ROGER A. MATHES.

REFERENCES CITED The following references are of record in the file of this patent:

' UNITED STATES PATENTS Number Name Date 2,146,669 Cramer Feb. 7, 1939 2,496,941

Hardman Feb. 7.1950 

1. A COMPOUND HAVING THE FORMULA 